Question

Carbon-14 has a half-life of 5,730 years. How long will it take for 112.5 g of a 120.0 g sample to decay radioactively?

Answer 1

`22920` years

Explanation:

The half life of a substance is the time taken for the amount of a substance present to halve. If 112.5g has decayed we have 7.5g left. To get to 7.5g we need to halve 120g four times.

`120rarr60rarr30rarr15rarr7.5`

The total time elapsed in this time will be four times the half life, so

`T = 4*t_(1/2) = 4*5730 = 22920` years